As it turns out, it was not Game Informer who made that error, but 343 Industries studio head John Holmes who relayed the wrong information to the magazine. Now he has stated his mistake in a post on the Halo Waypoint website:

"I need take a moment to make an important correction on something we miscommunicated in the story. I misspoke during the interview when stating that online co-op campaign would be supported with an Xbox Live Silver account. Co-op campaign will require Xbox Live Gold to play. I want to extend my sincere apologies to our fans, and to Game Informer, for this error and any confusion it has caused."

Holmes added that all copies of Halo 5: Guardians will include a code for a 14-day free trial of Xbox Live Gold. The company will reveal more information about the game next week at E3 2015, including a new and top secret multiplayer mode.